Gun construction for gas blast spraying heat-fusible materials



March 26, 1946. A. P. SHEPARD 2,397,165

GUN CONSTRUCTION FOR GAS BLAST SPRAYIFNG HEAT-FUSIBLE MATERIALS FiledOct. 25, 1943 3 Sheets-Sheet 1 March 26, 1946. A. P. SHEPARD 2,397,165

GUN CONSTRUCTION FOR GAS BLAST SPRAYING HEAT-FUSIBLE MATERIALS FiledOct. 25, 1943 3 Sheets-Sheet 2 March 26, 1946. A. P. SHEPARD 2,397,165

GUN CONSTRUCTIQN FOR GAS BLAST SPRAYING HEAT-FUSIBLE MATERIALS FiledOct. 25, 1943 3 Sheets-Sheet 5 Patented Mar. 26, 1946 GUN CONSTRUCTIONFOR GAS BLAST SPRAYING HEAT-FUSIBLE MATERIALS Arthur P. Shepard,Flushing. N. Y., assignor to Metallizing EnglneeringCo Inc.. Long IslandCity, N. Y.. a corporation of New Jersey Application October 25, 1943,Serial No. 507,528

' (Cl. til-12.2)

12 Claims.

This invention relates to improvements in gun construction for gas blastspraying heat-fusible materials. Heat-fusible material spray guns of thegas blast type are devices in which such material is fed into a meltingzone in which it is melted, bein thereafter expelled from the sun insubdivided form by a blast of air or other gas. The materials to besprayed may be fed into the melting zone either in the form of a rod orWire or in the form of powder. A mixture of fuel gas and combustionsupporting gas such as a mixture of acetylene or propaneand air oroxygen is fed to the melting zone through suitable jets which dischargethe combustible gas mixture which when ignited causes the melting of themetal. When powder is used, the same may not always be completely meltedas in some cases only some of the powder is melted, or some of theparticles of powder may be only partially melted or heat softened. Incases where a wire or rod is used, ai or other gas is forcefullydirected against the molten material at the tip of the rod or wire insuch manner that it impinges sharply against the tip to therebysubstantially blast the material into fine particles. The constructionof heat-fusible material spray guns of the gas blast type usuallyincludes a combustible-gas nozzle or burner tip which is provided with amaterial feeding conduit and a multiple number of combustible-gas jets,substan tially surrounding the axis of the feeding conduit, and a blastgas nozzle surroundin the combustible-gas nozzle and the feedingconduit. It is to such construction that the invention primarilyrelates.

Spray guns of the above described type are well known for the sprayingof metal, and for convenience the following description is made inconnection with metal spray gun constructions, it being understood thatthe principles of the invention are applicable to constructions usingother heatiusible materials, as for instance, plastics.

The hitherto used spray guns of the gas blast type. in which theheat-fusible material to be prayed is for instance metal. are ofrelatively low spraying speed and efliclency and are subject to thedanger of backnring. i. an ignition of a combustible gas mixture insidethe gas lets or the gas passages. Guns of t p r q ire for satisfactoryoperation th accurate maintenance of a predetermined pressurerelationship between the fuel gas an the combustion supporting gas. Thishas required that accurate regulators be used and that considerable carebe exercised by the operator in obtaining and maintaining the properpressure relationship between the two gases. If this proper pressurerelationship is not maintained even a relatively slight change in thepressure of either the combustible or the combustion supporting gas orboth will cause the flame at the tip of the combustible-gas nozzle tobecome unbalanced in that either there is an excess of fuel gas or anexcess of combustion supportin gas, according to the direction of theunbalance. This unbalanced flame condition causes greatly reducedspraying speeds and loss of efiiciency and in some cases causesbackfiring or the flame into the combustible-gas nozzle. Anotherdisadvantage of hitherto used metallizing guns is the fact that theyrequire a supply of fuel gas at a relatively high pressure and if not sosupplied with high pressure fuel gas, will I either not operate at allor will operate with materially reduced spraying speeds. on the otherhand, it is often disadvantageous to supply fuel gas to a metallizinggun at high pressure. For instance, as is well known. the use ofacetylene above a pressure of fifteen pounds per square inch gauge isconsidered hazardous because of the danger of disassociation of theacetylene. Further, some gases are not normally supplied at highpressure. Natural gas and coal gas for example, which are sometimes usedfor metallizin guns. are usually supplied at relatively low pressures.For this reason, when these gases are used for metallizing guns, it hasin the past been necessary that elaborate and expensive compressorequipment be installed between the gas source and the metallizing gun toraise the gas pressure to that required by the gun.

One object of this invention comprises, inter alia, a heat-fusiblematerial spray gun of the gas blast type construction which overcomesthe foregoing and other disadvantages.

A further object of this invention is a heat-fusible material blast gasspray gun construction which permits use of a combustion supportinggasat a relatively high pressure and a fuel gas at a relatively lowpressure.

Another object of this invention is a gun construction of the typereferred to which is comparatively little sensitive to relatively largevariations in the pressures of either one or both of the fuel gas andthe combustion supporting gas, 1. e.: a gun in which the relativequantitative relation between the fuel gas and the combustion supportinggas in the flame changes relatively little with a relatively large changin their relative Dressures.

Still another oblect of the invention is a heatfusible material spraygun construction of the gas blast type having a reduced tendency to backfire and reduced tendency to be damaged or burned if a backfire shouldoccur.

These and still further objects of the inven tion will be more fullyunderstood from the following description read in condunction with thedrawings illustrating preferred embodiments of the structure inaccordance with the invention in which- Fig. 1 is a central sectiontaken longitudinally through the gas head part of a metallizing gun inaccordance with my invention;

Fig. 2 represents a section through the part of the metallizing gunshown in Fig. 1 in the plane II-II;

Fig. 3 is another section of the part of the metallizing gun shown inFig. -1 taken through the plane IIIIII;

Fig. 4 is a view of the part of the metallizing gun shown in Fig. Iviewed in the direction IV-IV:

Fig. 5 is a section taken longitudinally through the gas head part of ametallizing gun in accordance with my invention showing certain feedconduit modifications Fig. 6 is a longitudinal section of one element ofa metallizing gun in accordance with my invention showing a preferredembodiment;

Fig. 7 is a view of the element shown in Fig. 6 from the directionVII-VII;

Fig. 8 is a longitudinal section of one element of a metallizing gun inaccordance with my invention showing a further preferred embodiment ofmy invention; and

Fig. 9 is a section of one element showing a still further embodiment ofmy invention.

Referring to Fi s. 1. 2, 3 and 4. numeral i desi nates the metal to besprayed which is shown in the form of a rod or wire. 2 is acombustibleas nozzle throu h which pass combustible-gas lots 3.Combustible-gas nozzle tin portion 2 is mounted on gas seat plug ornozzle rear portion 4 and is seatedwith a gas ti ht seal at seat 5 heldsecurely in place by nut 8 which screws onto threads I on 384: seat plug4. Gas seat plu 4 is constructed with a taper plug section 8 which fitsinto and seats with the taper seat in as head 9 being held securely inplace by means of nut it! wh ch sc ews onto threads Ii on the extendings ank of g s seat plug 4. Nut i is recessed to form space for packing I2which is compressed ti h ly a ainst the shank of gas seat plug 4 and theface of gas head 8 so as to form a gas ti ht seal between head 8 and theshank of as seat lug 4.

Gas seat plug 4 is provided with annular surfaces defining with theinner surfaces oi as hea 9 as mani olds i3 and i4. Manifold i4 extendsinto a relatively narrow extension roove I8 which extends inwardly i.e.: toward the axis of gas seat plug 4. Gas .iets I are provided in assent plug 4 and extend from man fold iii to the mar-- rowin portion ongroove extension l8 of manifold l4. Gas ,iets I! are provided in gasseat plug 4 and extend from groov extension i8 to the face of the plugat seat 5. Gas jets i! are at least at their inlet of largercross-sectional area than jets l I at least at their outlet.

Gas jets I1 and combustible-gas jets 3 are so located that theirconnecting ends are in substantial alignment at seat I; to insure thisalignment a dowel pin I. may be provided in the face of gas seat plug 4to match with a corresponding hole provided in combustible-gas nozzletip portion 2.

A gas duct i0 is provided in gas head 9 and leads from a source ofrelatively high pressure gas (not shown) to gas manifold i3. Gas duct 20leads from a source of relatively low pressure gas (not shown) andconnects with the gas manifold l4 and groove extension I. Compressed gasblast duct 2| leads into compressed blast gas duct 22. Duct 22 emergesat its outer end at 23 at the face of gas head 9. A blast gas nozzle oncap 24 is provided which screws onto gas head 8 at threads 25 and formsa blast gas chamber 28.

When using metal in the form of rod or wire as is illustrated in Fig. 1a relatively hard guide bushing 21 may be provided in combustible-gasnozzle tip portion 2.

In operation, a fuel gas. a combustion supporting gas and a blast gasare supplied to the gas head 9 from appropriate supply sources (notshown). In the most preferred method of operation a combustionsupporting gas such as air or o ygen at relatively high pressure issupplied to duct l9 and a fuel (such as acetylene, propan or the like)at relatively low pressure is supplied to duct 20. The combustionsupporting gas flows through duct l9 into manifold l3 and thence throughgas jets I5, across groove extension i8 and into gas jets I'I. the endsof which are in substantially gas flow directional alignment with theoutlet ends of gas jets [5. Fuel gas flows through duct 20 into themanifold M and continues if/s flow into groove extension I 6 which. asillustrated. preferably extends down and beyond inlet end: of jets l1,freely supplying fuel gas thereto. The relatively high velocity of thegas passing from gas jets it across groove extension IS and into gasjets i1 causes fuel gas to flow from groove extension [8 into gas jetsI! where it mixes with the combustion supporting gas. The mixture offuel and combustion supporting gases flows from gas jets I! throughcombustible-gas jets 3 and out of the end of gas nozzle tip portion 2where combustion takes place. The heat formed by the combustion of thegases in front of the combustible-gas nozzle tip portion 2 melts thewire I which is fed substantially continuously into the flame. The blastgas which may, for instance be air, flows through duct 2| and duct 22and emerges at 23 from gas head 9 into blast gas chamber 26 whence it isdirected by blast gas nozzle 24 against the tip of the molten wire i tofinelv divide and propel the metal.

While in the illustration just given, the combustion supporting gas wasconsidered at high pressure, the construction in accordance with thisinvention can also operate when the fuel gas is supplied at a relativelyhigh pressure and the combustion supporting gas at a relatively lowpressure. In this case, however, the fuel gas is supplied through ductl9 whence it flows into manifold l3, through gas jets ll. across grooveextension [8. and into gas jets l I. In this case, the combustionsupporting gas is supplied at relatively low pressure through duct 20 tomanifold i4 whence it passes into groove extension l8, flowing thence byreason of the relative gas velocity of the gas emerging from jets l5,into jets I! where it mixes with the fuel gas also entering jets H. Themixture of combustible and combustion supporting gases flows from letsi1 through gas jets 3 and out of combustible nozzle tip portion 2. theremainder of the operation being similar to that previously described.

Ii desired, material may be fed to the melting zone in granular formsuch as in the form of a powder. The structure in accordance with this-the multiple jets I! together.

invention using. for instance. a metal powder is shown in Fig. 5. Theconstruction is similar to that shown in Fig. 1 except that in this casethe metal powder conduit 28 has been connected by screwing it ontothreads 1 I to the back end of gas seat plug 4 so as to permit offeeding metal powder 29 through the central duct in gas seat plug 4 andcombustible-gas nozzle tip portion 2. The operation of the device issimilar to the case in which the metal was supplied in the form of awire as previously described, except that in this case it may only benecessary to heat soften or partially melt the metal in the flame.Furthermore, in this case the blast gas emerging from blast gas chamber28 and directed by blast gas nozzle 24 need only propel and need notnecessarily finely divide the metal being sprayed.

-One a: the primary advantages of the structure in accordance with myinvention is not only its greatly reduced tendency to backfire, i. e.:

burn back inside the jets, but also the reduced tendency for damage tooccur as the result of backflring, if this should occur. In previouslyknown constructions, when backfiring occurs the nozzle usually becomesirreparably damaged within a few seconds after backfiring and in manycases the gas head itself is burned out. With the construction inaccordance with this invention, damage from backflring is' extremelyunlikely. When backfiri'ng'does occur, the flame burns in gas jet I!because the combustible mix does not exist any further back. The volumeof the exhaust gases generated by the combustion so restricts the flowof both the fuel and combustion supporting gases that a very small flamein gas jets 11 results. Ordinarily this flame is so small that the heatwhich it produces is dissipated through the structure of gas seat plug 4and combustible-gas nozzle tip portion 2, and is carried away by thecooling effect of the blastof air or gas. in chamber 26 so that noburning out of the nozzle 'or other parts results.

With the structure shown in Fig. 1 it is possible for an individual jetto backfire and for the remaining jets to continue to function normally.This is sometimes an advantage as the spraying function can thencontinue despite the relative impairment due to the loss of one of themultiple number of jets. However, this can also be a disadvantagebecause the operator may not be aware that a jet has backfired. I havediscovered that a small channel provided'to connect the multiple jets ofthe mixed fuel and combustion supporting vantage.

Referring to Figs. 6 and '7, 4 represents a gas seat plug showing analternative form of my invention. This gas seat plug 4' is constructedsimilarly to gas seat plug 4 shown in Fig. l and has gas' jets I and i1and dowel pin l8. An annular groove 30 is provided in the seat connectinThis annular groove need not be and is preferably not large enough topermit the flow of very much' gas. For instance, it is preferable toconstruct the roove with a cross-section considerably smaller than thecross-section of one of the jets l1. The function of this groove is notto permitof the flow of gas under normal conditions but is to connectthe jets so that if any one of the jets should backfire then all of thejets will instantly backfire. With this construction, which is preferredfor ordinary metallizing use, the operator will known instantly if abackfire should occur..

.gases will alleviate this last' mentioned disad- V An alternativestructure in accordance with my invention is shown in Fig. 8 whichillustrates a gas seat plug 4". This plug is constructed similarly tothe gas seat plug 4 illustrated in Fig. 1 and has gas jets it". In thiscase however, gas jets II" are constructed larger at their inlet than attheir outlet end. In this construction, the jets II" have asmooth andpreferably long taper and the taper is most preferably curved somewhatso that the slope of the taper diminishes from the inlet to the outletend.

Another alternative structure in accordance with my invention isillustrated in Fig. 9 in which gas seat 4' is similar to thoseillustrated in Figs. 1 and 8, except that jets I 5" are slightlytapered, the inlet ends being smaller and the outlet ends being larger.The amount of this taper depends upon the pressure differential betweenthe inlet and outlet end of the jets 15'" and should be so proportionedas to obtain the maximum velocity of gas emerging from jet I5. The gasjets I 1" may be tapered as shown and as described in connection withthe embodiment of my invention shown in Fig. 8 or they may be straightas shown in the embodiment of my invention shown in Fig. l.

In all cases, I prefer to round the edges slightly at the inlet end ofjets IS, l5, l5" and l5', although this is not necessary.

As previously discussed, it has been found desirable to havecombustible-gas jets 3 substantially in line with gas jets I1. I havediscovered that if the inlet ends of combustible-gas jets 3 are slightlylarger than the outlet ends of gas jets l'l, that the necessity foraccurate alignment is reducedand that no appreciable impairment ofefficiency results from a slight misalignment. I preferably make theinlet ends of combustiblegas jets 3 approximately 50 per cent larger onthe diameter than the diameter of the outlet ends of gas jets l1.

I preferably make combustible-gas jets 3, where they emerge from thecombustible-gas nozzle tip portion 2, either the same as, or slightlysmaller than the outlet ends of gas jets I1. I have found that with theinlet ends of combustible-gas jets 3 enlarged, it is possible to havethese jets out of line to a slight degree with gas jets II without toogreat an impairment of efllclency. With the inlet ends ofcombustible-gas jets 3 50 per cent larger on the diameter than theoutlet ends of gas jets 11, I prefer not to have these two jets out ofline by more than 25 per cent of the. diameter of the outlet ends of gasjets I'I.

While the structures shown in the illustrations are necessary specific,my invention applies broadly to the improvement in gun construction forgas blast spraying heat-fusible material and preferably metal whichessentially comprises at least one gas chamber, at least one first gasjet, first means for supplying one of 'a fuel gas and combustionsupporting gas at relatively high pressure to said first gas jet, atleast one second gas jet, dimensioned and shaped for substantially free,non-turbulent gas flow to the discharge end of said nozzle, leading fromsaid gas chamber with its inlet in open communication therewith andpositioned with its inlet in gas flow directional alignment with theoutlet pf said flrst igas jet, and second means for freely supplying theother of such fuel gas and combustion supporting gas at relatively lowpressure to said gas chamber.

, In using the structure in accordance with my combustion supportinggasand I prefer to use the oxygen at a relatively higher pressure thanthe fuel gas. -As oxygen may be compressed to any reasonable pressurewithout any appreciable danger, this makes it possible to maintain, in

connection with the structure in accordance with my invention, very highoutlet velocities of the of as much as eight pounds per square inch willcause only the same unbalance condition at the name which would becaused by an unbalwith previously known metallizing guns.

The foregoing description is furnished by way of illustration and not oflimitation, and it is therefore my intention that the invention belimited only by the appended claims or their equivalents wherein I haveendeavored to claim broadly all inherent novelty.

I claim:

1. In a gun construction for gas blast spraying heat-fusible materialhaving a combustible gas nozzle with at least one combustible gas jetdischarge end, means for continuously feeding heatfusible material to apoint in gas flow directional alignment with said discharge end, andmeans for directing an atomizing blast gas toward said point, theimprovement in combustible-gas nozzle for such gun which comprises atleast one gas chamber, at least one first gas jet, first means forsupplying one of a fuel gas and combustion supporting gas at relativelyhigh pressure to said first gas jet, at least one second gas jet ofinternally streamlined surface, dimensioned and shaped for substantiallyfree, non-turbulent gas flow to the discharge end of said nozzle,leading from said gas chamber with its inlet in open communicationtherewith and positioned with its inlet in gas fiow directionalalignment with the outlet of said first gas jet, and second means forfreely supplying the other of such fuel gas andcombustion supporting gasat relatively low pressure to said gas chamber.

2. In a gun construction in accordance with claim 1 inwhich said inletof said second gas iet is larger than the'outlet of said first gas jet.

3. In a gun construction for gas blast spraying heat-fusible materialhaving a combustible gas nozzle with at least one combustible gas Jetdischarge'end,- means for continuously feeding heatfusible material to apoint in gas flow directional alignment with said discharge end, andmeans for directing an atomizing blast gas toward said point. theimprovement in combustible-gas nozzle for such gun which comprises atleast one gas chamber, a multiple number of first gas Jets spaced aroundthe axis of the gas nmzle, first means for supplying one of a fuel gasand combustion sup-'- porting gas at relatively high pressure to each ofsaid first gas lets, a multiple number of second gas Jets, one for eachof said first gas Jets, each of internally streamlined surfacedimensioned and shaped for substantially vfree, non-turbulent gas flowto the discharge end of said nozzle, each leading from said gas chamberwith its inlet in open anced pressure of only 3 pounds per square inchcommunication therewith and each positioned with its inlet in gas flowdirectional alignment with the outlet of its first g let, and secondmeans for freely supplying the other of such fuel ga and combustionsupporting gas at relatively low pressure to said gas chamber, the inletof each second gas let being larger than the outlet of its first 8 l 4.In a gun construction according to claim 3 in which the inlet of eachsecond gas jet is larger than it outlet.

5. In a gun construction according to claim 3 in which the outlet ofeach first gas jet is larger than its smallest cross-sectional area.

6. In a gun construction for gas blast spraying heat-fusible materialhaving a combustible gas nozzle with at least one combustible gas Jetdischarge end, means for continuously feeding heatfusible material to apoint in gas fiow directional alignment with said discharge end, andmeans for directing an atomizing blast gas toward said point, theimprovement in combustible-gas nozzle for such gun which comprises asubstantially-annular manifold substantially concentrically arrangedwith respect to the axis of the gas nozzle, a multiple number of firstgas Jets spaced around said axis and each ending with its outlet in saidmanifold, first means for supplying one of a fuel gas and combustionsupporting gas at relatively high pressure to each of said first gaslets, a multiple number of second gas jets, one for each of said firstgas jets, each of internally stream lined surface dimensioned and shapedfor substantially free, non-turbulent gas fiow to the discharge end ofsaid nozzle, each leading from said manifold with its inlet in opencommunication therewith and eachpositioned with its inlet in gas flowdirectional alignment with the outlet of its first gas jet, and secondmeans for freely supplyin: the other of such fuel gas and combustionsupporting gas at relatively low pressure to said manifold. the inlet ofeach second gas jet bein larger than the outlet of its first gas jet.

7. In a gun construction according to claim '6 in which said manifoldextends across the inlet of each of said second gas jets to permit gasto fiow from said manifold into and from all sides oi said inlets.

8. In a gun construction according to claim 6 in which said manifold issubstantially defined by a groove in at least one of two mating conicalsurfaces of said nozzle, and in which said groove extends across theinlet of each of said second gas Jets to permit gas to flow from saidmanifold into and from all sides of said inlets.

, 9. In a gun construction for gas blast sprayin heat-fusible materialhaving a combustible gas nozzle with at least one combustible gas jetdis-v charge end. means for continuously feeding heatfusible material toa point in gas fiow directional alignment with said discharge end, andmeans for-directing an atomizing blast gas toward said point. theimprovement in combustible-gas nozzle for such gun which comprises a gasnozzle rear portion including a multiple number of first gas Jets. firstmeans for suppLv ng one of a. fuel gas and combustion supporting gas atrelatively high pressure to each of said first gas jets, a multiplenumber of second gas jets, one for each of said first gas ietsiach ofinternally streamlined surface dimensioned and shaped for substantiallyfree, non-turbulent gas fiow to its outlet and each positioned with itsinlet in gas flow directional alignment with the outlet of its first gasjet, second means for freely supplying the other of such fuel gas andcombustion supporting 88s at relatively low pressure to the inlet ofeach second gas jet, the inlet of each second gas jet being larger thanthe outlet of its first gas jet, a gas nozzle tip portion removablymounted on said rear portion and a multiple number of third gas jets insaid tip portion, one for each of said second gas jets and inapproximate alignment therewith.

10. In a gun construction according to claim 9 in which the inlets ofsaid third gas jets are larger than the outlets of said second gas jets.

11. In a gun construction according to claim 9 in which a groove isprovided on at least one of the mating surfaces of said gasnozzle rearand tip portion substantially connecting all of said second gas jetoutlets and said third gas jet inlets.

12. In a gun construction for gas blast spraying heat-fusible materialhaving a combustible gas nozzle with at least one combustible gas jetdischarge end, means for continuously feeding heat-fusible material to apoint in gas flow directional alignment with said discharge end, andmeans for directing an atomizing blast gas toward said point, theimprovement in combustiblegas nozzle for such gun which comprises a gasnozzle rear portion, including a substantially annular first manifold,substantially concentrically arranged with respect to the axis of thegas nozzle and substantially defined by a groove in at least one of twomating conical surfaces of said nozzle, a multiple number of first Iasjets substantially evenly spaced around said axis and each ending withits outlet in said manifold, a substantially annular second manifold forsupplying one of a fuel gas and combustion supporting gas at relativelyhigh pressure to each of said first gas jets, a multiple number ofsecond gas jets, one for each of said first gas jets, each of internallystreamlined surface dimensioned and shaped for substantially free,non-turbulent gas flow, each leading from said first manifold with itsinlet in open communication therewith and each positioned with its inletin gas flow directional alignment with the outlet of its first gas jet,the outlet of each first gas jet being smaller than the inlet of itssecond gas jet, said first manifold extending across the inlet of eachsecond gas jet to permit gas to flow from said manifold into and fromall sides of said inlets. means for freely supplying the other ofsuch'fue1 gas and combustion supporting gas at relatively low pressureto said first manifold, and a gas nozzle tip portion, removably mountedon said gas nozzle rear portion. including a multiple number of thirdgas jets, one for each of said sec- 5 0nd gas jets and in approximatealignment therewith, and a groove on at' least one ofthe mating surfacesof said gas nozzle rear and tip portion substantially connecting all ofsaid second 0 gas jet outlets and said third gas jet inlets.

ARTHUR P. SHEPARD.

